class_docstr: A Tensorflow(Keras) Conlleval evaluator.
  Runs the conlleval script for given x and y inputs.
  Prints Conlleval F1 score on the end of each epoch.
  
  Args:
      x: features matrix
      y: labels matrix
      y_vocab (dict): int-to-str labels lexicon
      batch_size (:obj:`int`, optional): batch size
code: def __init__(self, x, y, y_vocab, batch_size=1):
      super(ConllCallback, self).__init__()
      self.x = x
      self.y = y
      self.y_vocab = {v: k for k, v in y_vocab.items()}
      self.bsz = batch_size
  
file_path: nlp-architect/nlp_architect/nn/tensorflow/python/keras/callbacks.py
imports: from __future__ import division
  from __future__ import print_function
  from __future__ import unicode_literals
  from __future__ import absolute_import
  import tensorflow
  from nlp_architect.utils.metrics import get_conll_scores
label_desc: Use image node_id 1 to create a new ConllCallback object from inherited base classes: tf.keras.callbacks with example: obj = ConllCallback(x, y, y_vocab, batch_size)